Telecommunication systems serve numerous subscribers with respective terminal services. Large private telecommunication systems can have in excess of 10,000 subscribers or stations, each with a respective terminal device or a plurality of such terminal devices. These private systems, also referred to herein as telecommunications networks, can be linked, for example, by the QSIG into an overall telecommunications system whose participants are limited in number only by the maximum permissible length of the call numbers or subscribers numbers, i.e. the telephone number assigned to the terminal device.
Telecommunications networks of such large size only require a sufficient breadth of the spectrum of the field in which they are operated and if it is desirable to expand smaller telecommunications systems further, server based applications like CTI (Computer Telephony Integration) CRM (Customer Relations Management) and Call Center Techniques are used.
The increase in the utilization of telephone networks can be implemented differently at different costs. For example, server based applications and telephone exchange improvements require high capital cost which may be uneconomical in the case of smaller systems so that such improvements usually are not implemented in smaller telecommunications networks. For telecommunications networks which are linked to serve many customers, the distribution of the cost may make improvements tolerable by spreading the cost of the improved features over the number of subscribers. Two approaches of this type are represented by the Centrex service in an open network of Deutschen Telekom AG and the multicompany approach of a private telecommunications service.
In the Centrex service typical performance features are applied centrally for private telephone networks with open network drivers for many customers. The service utilizes the characteristics of a private network and characteristics of open networks. The network intelligence, namely, the control of performance or capability characteristics is in the open network and the interface between the open network and the private network which is a virtual network having a function of a gateway in an open gateway.
The multicompany approach is based upon a private network concept with communication at a specific location with the telephone network. In one application the communication system of a building or a communication system driven by a network driver is used as the basis. Such network drivers can be operated for example, by a company like the present assignee or the Regus Corporation of the United Kingdom.
The network technology in the private network is located at the campus and the interface to the open network is at the campus. The private network can in turn include a plurality of private telephone networks itself. A number of independent customers or served systems can utilize each telephone network independently. An administrator of the network drive of the system which operates the telephone network implements the performance features and as selected by the customer or utilizing enterprise and ensures that the subscribers or users of that customer or company are prepared.
The private telephone networks described in the literature however are not truly capable of satisfying all of the requirements of such systems and it therefore is not possible to provide for each individual customer or served company individually or simultaneously all combinations of performance or capability enhancements.
For that reason the operator of the campus network generally will provide packages of capability or performance features which are simultaneously offered and operated.
In one such system the number of firms which can be handled is limited to 64 and the telephone network is incapable of recognizing the idea or motion of the firm or the customer or the served enterprise. There is therefore a limitation in the number of customers which can be served or the number of performance features which can be made available. The performance features must therefore be compromised for example, in the formation of traffic groups.
The term “client” and the term “customer”, as far as telephone services are concerned can be equivalent and each will generally refer to a plurality of subscribers, each having a terminal device and, from the perspective of the apparatus, a singular subscriber connection line connected to that device and identified in the apparatus to mean that device and the subscriber. In communications it is customary to refer to the subscriber and the terminal device interchangeably. With the aid of a calling number plan, the relationship between the subscriber line of a terminal device and an internal call number of the subscriber is made.
Furthermore, it is known to operate a telecommunications apparatus in an exchange of such telecommunications apparatuses, i.e. a number of telecommunications apparatuses so linked together that the exchange is formed by digital connection lines between the individual telecommunications apparatuses.
As the protocol enabling communication between these apparatuses and through these lines, either a standardized protocol (QSIG, DPNSS1), or a proprietary protocol (TNET, CORNET, . . . ), may be used. Telecommunications apparatuses in an exchange have devices to charge the use of the line per connection and for connection duration. The prior art provides an exchange of private telecommunications apparatuses each of which might have its own client.
Systems which are customer-based utilizing private telecommunication apparatuses are limited with respect to the mobility of the subscriber or the terminal device since such mobility is usually not part of the system plan and if present, must use an existing radio network. It is common, therefore, for mobile terminal devices to use a different network from the fixed communication system even of a specific client or enterprise. Any attempt to integrate the two in the past has resulted in limitations in utility of one or the other.
The drawbacks of prior systems can be seen from the following scenario:
An outside worker of a firm requires a completely different technological office environment from that of an inside worker of the firm of one located at the office of the firm. In some cases he may be located in a strange office environment and in that case must use the telecommunication equipment of the firm at which he is located and its services and functions. He cannot contact his clients with normal short internal and private call numbers but must use public and long calling numbers. His colleagues cannot contact him with short internal numbers but must use longer public call numbers. If he must use the telefax, he cannot normally use the numbers which his firm may provide. If he requires a data connection for a PC or other device, again he must use numbers which are foreign to him.
If he is not located in a foreign fixed environment but is in an automobile, bus, truck, house or construction trailer or the like, he must use a portable unit, and for example a PDA or PC which can be connected to the portable unit. In many cases such portable units may not even operate at a particular location. When his colleague or others contact him or he them is through short internal numbers, public long numbers must be used.